Field of the Invention
This invention relates to a gas discharge (plasma) device wherein an ionizable gas is confined within an enclosure and is subjected to sufficient voltage(s) to cause the gas to discharge. This invention particularly relates to the use of microspheres containing ionizable gas in a plasma display panel (PDP).
In a gas discharge plasma display, a single addressable picture element is a cell, sometimes referred to as a pixel. The cell element is defined by two or more electrodes positioned in such a way so as to provide a voltage potential across a gap containing an ionizable gas. When sufficient voltage is applied across the gap, the gas discharges and produces light. In an AC gas discharge plasma display, the electrodes at a cell site are coated with a dielectric. The electrodes are generally grouped in a matrix configuration to allow for selective addressing of each cell or pixel.
To form a display image, several types of voltage pulses may be applied across a plasma display cell gap. These pulses include a write pulse, which is the voltage potential sufficient to ionize the gas at the pixel site. A write pulse is selectively applied across selected cell sites. The ionized gas will produce visible light, or UV light which excites a phosphor to glow. Sustain pulses are a series of pulses that produce a voltage potential across pixels to maintain ionization of cells previously ionized. An erase pulse is used to selectively extinguish ionized pixels.
The voltage at which a pixel will ionize, sustain, and erase depends on a number of factors including the distance between the electrodes, the composition of the ionizing gas, and the pressure of the ionizing gas. Also of importance is the dielectric composition and thickness. To maintain uniform electrical characteristics throughout the display it is desired that the various physical parameters adhere to required tolerances. Maintaining the required tolerance depends on cell geometry, fabrication methods and the materials used. The prior art discloses a variety of plasma display structures, a variety of methods of construction, and a variety of materials.
Examples of gas discharge (plasma) devices contemplated in the practice of this invention include both monochrome (single color) AC plasma displays and multi-color (two or more colors) AC plasma displays.
Examples of monochrome AC gas discharge (plasma) displays contemplated in the practice of this invention are well known in the prior art and include those disclosed in U.S. Pat. No. 3,559,190 issued to Bitzer et al., U.S. Pat. No. 3,499,167 (Baker et al), U.S. Pat. No. 3,860,846 (Mayer) U.S. Pat. No. 3,964,050 (Mayer), U.S. Pat. No. 4,080,597 (Mayer) and U.S. Pat. No. 3,646,384 (Lay) and U.S. Pat. No. 4,126,807(Wedding), all incorporate herein by reference.
Examples of multicolor AC plasma displays contemplated in the practice of this invention are well known in the prior art and include those disclosed in U.S. Pat. No. 4,233,623 issued to Paviiscak, U.S. Pat. No. 4,320,418 (Paviiscak), U.S. Pat. No. 4,827,186 (Knauer, et al.), U.S. Pat. No. 5,661,500 (Shinoda et al.), U.S. Pat. No. 5,674,553 (Shinoda, et al.), U.S. Pat. No. 5,107,182 (Sano et al.), U.S. Pat. No. 5,182,489 (Sano), U.S. Pat. No. 5,075,597 (Salavin et al), U.S. Pat. No. 5,742,122 (Amemiya, et al.), U.S. Pat. No. 5,640,068 (Amemiya et al.), U.S. Pat. No. 5,736,815 (Amemiya), U.S. Pat. No. 5,541,479 (Nagakubi), U.S. Pat. No. 5,745,086 (Weber) and U.S. Pat. No. 5,793,158 (Wedding), all incorporated herein by reference.
In addition, this invention may be practiced in a DC gas discharge (plasma) display, for example as disclosed in U.S. Pat. No. 3,886,390 (Maloney et al.), U.S. Pat. No. 3,886,404 (Kurahashi et al.), U.S. Pat. No. 4,035,689 (Ogle et al.) and U.S. Pat. No. 4,532,505 (Holz et al.), all incorporated herein by reference.
In the practice of this invention, the microspheres may be used in any plasma display panel (PDP) structure. The PDP industry has used two different AC plasma display panel (PDP) structures, the two-electrode columnar discharge structure and the three-electrode surface discharge structure.
The two-electrode columnar discharge display structure is disclosed in U.S. Pat. No. 3,499,167 (Baker et al) and U.S. Pat. No. 3,559,190 (Bitzer et al.) The two-electrode columnar discharge structure is also referred to as opposing electrode discharge, twin substrate discharge, or co-planar discharge. In the two-electrode columnar discharge AC plasma display structure, the sustaining voltage is continuously applied between an electrode on a rear or bottom substrate and an opposite electrode on the front or top viewing substrate. The gas discharge takes place between the two opposing electrodes in between the top viewing substrate and the bottom substrate.
The columnar discharge structure has been widely used in monochrome AC plasma displays that emit orange or red light from a neon gas discharge. Phosphors may be used in a monochrome structure to obtain a color other than neon orange.
In a multi-color columnar discharge (PDP) structure as disclosed in U.S. Pat. No. 5,793,158 (Wedding), phosphor stripes or layers are deposited along the barrier walls and/or on the bottom substrate adjacent to and extending in the same direction as the bottom electrode. The discharge between the two opposite electrodes generates electrons and ions that bombard and deteriorate the phosphor thereby shortening the life of the phosphor and the PDP.
In a two electrode columnar discharge PDP as disclosed by Wedding 158, each light emitting pixel is defined by a gas discharge between a bottom or rear electrode x and a top or front opposite electrode y, each cross-over of the two opposing arrays of bottom electrodes x and top electrodes y defining a pixel or cell.
The three-electrode multi-color surface discharge AC plasma panel structure is widely disclosed in the prior art including U.S. Pat. Nos. 5,661,500 and 5,674,553, both issued to Tsutae Shinoda et al of Fujitsu Limited; U.S. Pat. No. 5,745,086 issued to Larry F. Weber of Plasmaco and Matsushita; and U.S. Pat. No. 5,736,815 issued to Kimio Amemiya of Pioneer Electronic Corporation, all of which are incorporated herein by reference.
In a surface discharge PDP, each light emitting pixel or cell is defined by the gas discharge between two electrodes on the top substrate. In a multi-color RGB display, the pixels may be called sub-pixels or sub-cells. Photons from the discharge of an ionizable gas at each pixel or sub-pixel excite a photoluminescent phosphor that emits red, blue, or green light.
In a three-electrode surface discharge AC plasma display, a sustaining voltage is applied between a pair of adjacent parallel electrodes that are on the front or top viewing substrate. These parallel electrodes are called the bulk sustain electrode and the row scan electrode. The row scan electrode is also called a row sustain electrode because of its dual functions of address and sustain. The opposing electrode on the rear or bottom substrate is a column data electrode and is used to periodically address a row scan electrode on the top substrate. The sustaining voltage is applied to the bulk sustain and row scan electrodes on the top substrate. The gas discharge takes place between the row scan and bulk sustain electrodes on the top viewing substrate.
In a three-electrode surface discharge AC plasma display panel, the sustaining voltage and resulting gas discharge occurs between the electrode pairs on the top or front viewing substrate above and remote from the phosphor on the bottom substrate. This separation of the discharge from the phosphor minimizes electron bombardment and deterioration of the phosphor deposited on the walls of the barriers or in the grooves (or channels) on the bottom substrate adjacent to and/or over the third (data) electrode. Because the phosphor is spaced from the discharge between the two electrodes on the top substrate, the phosphor is subject to less electron bombardment than in a columnar discharge PDP.